Fluorosilicone heat cured elastomeric (HCE) compounds are used in automotive applications to provide gaskets, o-rings and diaphragms. When used as a component of an automobile or truck engine, these materials must display good resistance to hydrocarbon fuels and oils by maintaining good sealing integrity under compression at the elevated temperatures experienced when the engine is operating. At the high temperatures created by an internal combustion engine, fluorosilicone elastomers undergo chain scission reactions with re-crosslinking. When this happens while the fluorosilicone material is under a compression load the material loses sealing performance as measured by compression set. The typical solution to this problem has been to minimize thermal degradation and thermal oxidative degradation by incorporating selected metal oxides either singly or as mixtures. Another approach has been to utilize a highly crosslinked polymer derived from a polymer having a high degree of unsaturation on the polymer backbone and adding a so-called co-agent which imparts resiliency under the removal of a deforming stress. These so-called co-agents are compounds which participate in the free radical cure of the polymer by tending to form more stable free radicals which impart a more extensive or higher state of cure.
A number of these types of compounds have been described and are employed to improve the cured physical property profile of hydrocarbon elastomers. Many of these materials have been used in silicone and fluorosilicone elastomers, e.g. triallylcyanurate, triallylisocyanurate, trimethyl propane trimethylacrylate (available commercially as Sartomer 350.RTM.), and tripropylene glycol diacrylate (available commercially as Sartomer 306.RTM.). While specific compounds such as zinc dimethylacrylate and zinc diacrylate are effective for improving adhesion between elastomers and metal substrates, the zinc tends to act as an agent to dehydrohalogenate fluorosilicone elastomers leading to formation of olefinic unsaturation which undergoes further crosslinking and thereby deleteriously affecting the compression set of the elastomer. While co-agents such as the Sartomer 350.RTM. or 306.RTM.) are effective for promoting crosslinking at levels above 0.5 parts per hundred parts elastomer composition, these materials tend to increase elastomer metal adhesion and this results in production problems because the elastomer sticks to the metal molds used to form the gasket, O-ring or diaphragm. Because of these problems it is highly desirable to find either a compound or a class of compounds that promote crosslinking in heat cured fluorosilicone rubbers without creating mold release problems during the forming step.